Pneumatic Tyre

ABSTRACT

A pneumatic tyre includes: a carcass structure with at least one carcass ply shaped in a substantially toroidal configuration, the opposite lateral edges of which are associated with respective right-hand and left-hand bead wires, each bead wire being enclosed in a respective bead, a belt structure including at least one belt layer applied in a circumferentially external position relative to the carcass structure; a tread band superimposed circumferentially on the belt structure including a radially outer layer designed to come into contact with the ground; and a pair of sidewalls applied laterally on opposite sides relative to the carcass structure. The tread band includes an elastomeric material obtained by cross-linking a cross-linkable elastomeric composition including: a) from 15 phr to 95 phr of at least one styrene-butadiene rubber; b) from 5 phr to 30 phr of at least one halogenated butyl rubber; c) from 0 phr to 60 phr of at least one diene rubber other than a); d) from 0.3 phr to 3.5 phr of at least one aminosilane containing at least one hydroxy group or hydrolysable group attached to the silicon atom of the silane; e) from 10 phr to 140 phr of at least one silica filler; and f) from 0.5 phr to 25 phr of at least one sulphur-containing silane with at least one hydroxy group or hydrolysable group attached to the silicon atom of the silane.

BACKGROUND OF THE INVENTION

The present invention relates to a pneumatic tyre, in particular forhigh performance.

Specifically, the present invention refers to a pneumatic tyrecomprising a carcass structure having at least one carcass ply, and atleast one annular reinforcing structure associated to the carcass ply, atread band made of an elastomeric material at a radially outer positionwith respect to the carcass structure, a belt structure interposedbetween the carcass structure and the tread band and a pair of axiallyopposite sidewalls on the carcass structure, wherein the tread band isprovided with a pattern comprising one or more longitudinal and/ortransversal grooves.

PRIOR ART

Tyre properties such as grip on wet surfaces and wear resistance, thatare of great importance for the handling and running stability of thevehicle, are determined, to a large extent, by the composition of thetread band rubber composition.

Grip is favoured by a read rubber compound having high hysteresis values(tan δ). On the other side, a tread rubber compound having lowhysteresis values shows improved wear resistance. A balance betweenthese properties is an issue.

Many attempts have been made to introduce halogenated butyl rubber intothe tread band composition so as to improve the tyre grip. However, theaddition of a halogenated butyl rubber (XIIR) to the tread bandcomposition, although improving the tyre grip, causes a concomitantreduction of the wear resistance. As reported, for example, by EP 1 111004, the poor wear resistance of butyl compounds is due to one or bothof the following causes: (i) poor interaction between the butylelastomer and filler, and (ii) low level of crosslinking compared topolybutadiene (BR) or styrene-butadiene rubbers (SBR).

EP 1 111 004 relates to filled butyl elastomer compositions, suitablefor tire treads and sidewall, comprising a halogenated butyl elastomerwith a filler, especially a mineral filler, such as silica, in thepresence of a silane having at least one hydroxy group or hydrolysablegroup attached to a silicon atom of the silane. The halobutyl elastomermay be a mixture with other elastomers. The halobutyl elastomer shouldconstitute more than 20% of any such mixture. The silane is preferablyan aminosilane or a sulphur-containing silane; the amount of the silanecompound or compounds used may be about 2 to 12 parts per hundred partsof filler. Examples are provided of elastomer compositions containing100 phr of halogenated butyl elastomer and from 3 phr to 12 phr of3-aminopropyl triethoxysilane or bis(triethoxysilyl-propyl)tetrasulfane.

EP 1 236 767 provides an elastomeric composition comprising naturalrubber, a halobutyl rubber, a mineral filler, preferably silica, and arubber-mineral filler bonding agent. The bonding agent can be a silaneor mixture of silanes. The silane has at least one hydroxy group orhydrolysable group attached to the silane. Particular silanes that canbe used include an aminosilane or a sulphur-containing silane. Theamount of the silane compound or compounds used may be about 2 to 12parts per hundred parts of filler. The halobutyl elastomer shouldconstitute more than 5% of any such mixture. It is preferred not to usefurther elastomers but to use the halobutyl elastomer and natural rubberas the sole elastomers. If further elastomers are to be used, however,then the further elastomer may be, for example, polybutadiene,styrene-butadiene or polychloroprene or an elastomer compound containingone or more of these elastomers.

SUMMARY OF THE INVENTION

The Applicant observed that the advantages possibly provided by ahalobutyl rubber to the tread band compound of a pneumatic tyre werestill too hindered by drawbacks for an effective, practical application.

In particular, the Applicant observed that a tyre tread band suitablefor wet or icy/snowed surfaces should be based on an elastomericcomposition balancing the following characteristics:

-   -   low hardness at low temperatures for ensuring a suitable grip;    -   high values of static modulus that favour the tyre handling;    -   high tan δ values that are correlated with good traction and        performance, in particular high tan δ at 0° C. for wet and        icy/snowed surfaces.    -   low abrasion.

In addition, processability of the elastomeric composition should besuitable for tyre production in terms of scorch time and Mooneyviscosity.

The Applicant found that a tyre for vehicles provided with a tread bandobtained by cross-linking a composition comprising styrene-butadienerubber, halogenated butyl rubber in an amount as defined hereinbelow,and an aminosilane in an amount as defined hereinbelow, shows improvedperformance on wet or icy/snowed surfaces in terms of grip, wearresistance and handling, thus enhancing the safety and comfort of thevehicle equipped with such tyre, even under extreme driving conditions.

Therefore, the present invention relates to a pneumatic tyre comprising:

-   -   a carcass structure with at least one carcass ply shaped in a        substantially toroidal configuration, the opposite lateral edges        of which are associated with respective right-hand and left-hand        bead wires, each bead wire being enclosed in a respective bead;    -   a belt structure comprising at least one belt layer applied in a        circumferentially external position relative to said carcass        structure;    -   a tread band superimposed circumferentially on said belt        structure comprising a radially outer layer designed to come        into contact with the ground; and    -   a pair of sidewalls applied laterally on opposite sides relative        to said carcass structure;        wherein said tread band includes an elastomeric material        obtained by cross-linking a cross-linkable elastomeric        composition comprising:        a) from 15 phr to 95 phr of at least one styrene-butadiene        rubber;        b) from 5 phr to 30 phr of at least one halogenated butyl        rubber;        c) from 0 phr to 60 phr of at least one diene rubber other than        a);        d) from 0.3 phr to 3.5 phr of at least one aminosilane        containing at least one hydroxy group or hydrolysable group        attached to the silicon atom of the silane;        e) from 10 phr to 140 phr of at least one silica filler; and        f) from 0.5 phr to 25 phr of at least one sulphur-containing        silane with at least one hydroxy group or hydrolysable group        attached to the silicon atom of the silane.

According to another aspect, the present invention relates to across-linkable elastomeric composition comprising:

a) from 15 phr to 95 phr of at least one styrene-butadiene rubber;b) from 5 phr to 30 phr of at least one halogenated butyl rubber;c) from 0 phr to 60 phr of at least one diene rubber other than a);d) from 0.3 phr to 3.5 phr of at least one aminosilane containing atleast one hydroxy group or hydrolysable group attached to the siliconatom of the silane;e) from 10 phr to 140 phr of at least one silica filler; andf) from 0.5 phr to 25 phr of at least one sulphur-containing silane withat least one hydroxy group or hydrolysable group attached to the siliconatom of the silane.

For the purposes of the present description and of the claims thatfollow, except where otherwise indicated, all numbers expressingamounts, quantities, percentages, and so forth, are to be understood asbeing modified in all instances by the term “about”. Also, all rangesinclude any combination of the maximum and minimum points disclosed andinclude any intermediate ranges therein, which may or may not bespecifically enumerated herein.

For the purposes of the present description and of the claims, the term“phr” means the parts by weight of a given component of the elastomericcomposition per 100 parts by weight of the elastomeric base.

According to a preferred embodiment, the elastomeric compositioncomprises from 75 phr to 93 phr of a styrene-butadiene rubber a)(hereinafter also referred to as “SBR).

In the present description an claims, as “styrene-butadiene rubber” or“SBR” is meant a styrene/1,3-butadiene random copolymer typicallycomprising from 55 wt % to 95 wt % of 1,3-butadiene.

According to a preferred embodiment, the elastomeric compositioncomprises from 7 phr to 25 phr of a halogenated butyl rubber b).

Preferably, the halogenated butyl rubber according to the invention is achlorinated or brominated butyl rubber. Brominated rubbers areparticularly preferred.

Advantageously, halogenated butyl rubbers suitable for the presentinvention are obtained by halogenation of butyl rubber, that is acopolymer of isobutylene and at least one comonomer selected from C₄ toC₆ conjugated diolefins, preferably isoprene; and alkyl-substitutedvinyl aromatic comonomers such as C₁-C₄-alkyl substituted styrene. Oneexample that is commercially available is halogenated isobutylenemethylstyrene copolymer (BIMS) in which the comonomer isp-methylstyrene.

Preferably, isoprene is present in an amount of from 1 wt % to 3 wt %and isobutylene is present in an amount of from 97 wt % to 99 wt %.

The halogen content of said rubbers preferably ranges from 0.5 wt % to 4wt %, preferably from 0.75 wt % to 3 wt % of halogen based on thehalogenated butyl polymer.

Preferably, the halogenated butyl rubber has a viscosimetric averagemolecular weight comprised between 150,000 and 1,500,000 and a molarunsaturation comprised between 0.5% and 15%.

A stabilizer may be added to the halogenated butyl rubber. Suitablestabilizers include calcium stearate and epoxidized soybean oil,preferably used in an amount of in the range of from 0.5 to 5 parts byweight per 100 parts by weight of the halogenated butyl rubber.

Examples of suitable halogenated butyl rubbers include Bayer® Brominatedbutyl BB2040 and BB2030, commercially available from Bayer. Bayer®Brominated butyl BB2040 has bromine content of 2.0±0.3 wt %. Bayer®Brominated butyl BB2030 has bromine content of 1.8±0.2 wt %.

Examples of suitable chlorinated butyl rubbers include Bayer®Chlorobutyl CB1240, also commercially available from Bayer. Bayer®Chlorobutyl CB 1240 has chlorine content of 1.25±0.1 wt %.

According to a preferred embodiment, the elastomeric compositioncomprises from 0 phr to 30 phr of a diene rubber c), more preferably c)is absent.

Examples of diene rubbers c) which are useful for the purpose of theinvention are: polyisoprene, e.g. cis-1,4-polyisoprene (natural orsynthetic, preferably natural rubber, NR) and 3,4-polyisoprene;polybutadiene (in particular polybutadiene with a 1,4-cis content of atleast 80%); isoprene/isobutene copolymers; 1,3-butadiene/acrylonitrilecopolymers; styrene/isoprene/1,3-butadiene copolymers;styrene/1,3-butadiene/acrylonitrile copolymers; or mixtures thereof.

According to a preferred embodiment, the elastomeric compositioncomprises from 1 phr to 3 phr of an aminosilane d).

Advantageously, the content in aminosilane d) is tailored on the contentin halogenated butyl rubber b). The aminosilane d), owing to thenucleophilic nature thereof, reacts with the halogenated butyl rubber,and provides a “bridge” between such rubber and the silica filler e),thus achieving a compatibilization effect between the halogenated butylrubber b) and the other elastomeric composition components.

Advantageously, in the elastomeric composition of the invention theweight ratio between b) and d) components is of from 2 to 12, preferablyof from 5 to 8.

In the present description and claims, as “hydrolysable group” is meanta group that is able to hydrolyse to yield a hydroxy group on thesilicon atom. As examples of such hydrolysable groups there arementioned particularly alkoxy groups having up to six carbon atoms,especially ethoxy and methoxy groups. These and other hydrolysablegroups are discussed hereinbelow.

Preferably, an aminosilane d) useful for the present invention has thefollowing formula (I)

wherein:R₁, R₂ and R₃, which may be identical or different, are selected fromhydrogen, hydroxy, C₁-C₈ alkoxy groups, C₁-C₁₈ alkyl groups, C₆-C₂₀ arylgroups, C₇-C₃₀ alkylaryl or arylalkyl groups, with the proviso that atleast one of the groups R₁, R₂ and R₃ represents an hydroxy or anhydrolysable group;R₄ is selected from linear or branched C₁-C₁₈ aliphatic chains groups,C₆-C₂₀ arylene groups, said arylene groups optionally being substitutedwith C₁-C₈ aliphatic groups;R₅ and R₇, which may be identical or different, are selected fromhydrogen, C₁-C₁₈ alkyl groups; or, when R₅ and R₇ are other thanhydrogen, they may form, together with the nitrogen atoms to which theyare attached, 5- or 6-membered heterocyclic rings;R₆ is chosen from linear or branched C₁-C₁₈ alkylene groups, C₆-C₁₄arylene groups, arylene groups optionally substituted with C₁-C₁₈ alkylgroups, C₇-C₃₀ alkylenearylene or arylenealkylene groups, C₃-C₃₀cycloalkylene groups, said cycloalkylene groups optionally beingsubstituted with C₁-C₁₈ alkyl groups;n is a integer from 0 to 5.

In the aminosilane of formula I, it is preferred that all of R₁, R₂ andR₃ are hydrolysable groups, in particular C₁-C₈ alkoxy groups, morepreferably C₁-C₃ alkoxy groups. Optionally, said alkoxy groups show thealkyl chain interrupted by oxygen atoms, such as CH₃OCH₂O—,CH₃OCH₂OCH₂O—, CH₃(OCH₂)₄O—, CH₃OCH₂CH₂O—, C₂H₅OCH₂O—, C₂H₅OCH₂OCH₂O—,or C₂H₅OCH₂CH₂O—.

Non-limiting examples of R₁, R₂ and R₃ that are not hydrolysable includeC₁₋₁₀ alkyl, C₂₋₁₀ mono- or di-unsaturated alkenyl, and phenyl.

Preferably, R₄ is a C₁-C₃ aliphatic chain, more preferably a C₁-C₃alkylene chain.

Preferably, R₇ is hydrogen.

Preferably, n is 0,

Suitable aminosilanes of formula I include, but are not limited to2-aminoethyl-trimethoxysilane, 2-aminoethyl-triethoxysilane,2-aminoethyl-tripropoxysilane, 2-aminoethyl-tributoxysilane,3-aminopropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane,3-aminopropylmethyl-diethoxysilane,N-2-(vinylbenzylamino)-ethyl-3-aminopropyl-trimethoxysilane,N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N-2-(aminoethyl)-3aminopropyltris(2-ethylhexoxy)silane,3-aminopropyl-diisopropyl-ethoxysilane,N-(6-aminohexyl)-aminopropyl-trimethoxysilane,4-aminobutyl-triethoxysilane, 4-aminobutyldimethyl-methoxysilane,triethoxy-silylpropyl-diethylenetriamine,3-aminopropyltris-(methoxyethoxyethoxy)silane,N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane,N-2-(aminoethyl)-3-aminopropyltris(2-ethylhexoxy)-silane,3-aminopropyldiisopropyl-ethoxysilane,N-(6-aminohexyl)aminopropyl-trimethoxysilane,4-aminobutyl-triethoxysilane, and(cyclohexylaminomethyl)-methyl-diethoxysilane.

3-Aminopropyl-triethoxysilane (AMEO) is the most preferred.

According to a preferred embodiment, the elastomeric compositioncomprises from 40 phr to 110 phr of silica filler e).

Advantageously, the silica is a pyrogenic silica or, preferably, aprecipitated silica, with a BET surface area (measured according to ISOstandard 5794/1) of from 50 m²/g to 500 m²/g, preferably from 70 m²/g to200 m²/g.

Suitable silica fillers are available under the trademarks HiSil® 210,HiSil® 233 and HiSil® 243 from PPG Industries Inc. Also suitable areVulkasil® S and Vulkasil® N, from Bayer AG, and Zeosil® from RhodiaSilica System.

Optionally, the elastomeric composition may comprise at least one carbonblack reinforcing filler. Advantageously, the carbon black reinforcingfiller is selected from those having a surface area of not less than 20m²/g (determined by CTAB absorption as described in Standard ISO6810:1995).

Said carbon black reinforcing filler can be present in the elastomericcomposition in an amount of from 20 phr to 90 phr.

According to a preferred embodiment, the elastomeric compositioncomprises from 5 phr to 15 phr of a sulphur-containing silane f).

Examples of suitable sulphur-containing silanes include compounds offormula (II)

(R)₃Si—C_(n)H_(2n)—X  (II)

wherein the groups R, which may be identical or different, are selectedfrom: hydroxy, alkyl, alkoxy or aryloxy groups or from halogen atoms, oncondition that at least one of the groups R is a hydroxy, alkoxy oraryloxy group; n is an integer between 1 and 6 inclusive; X is a groupselected from: nitroso, mercapto, amino, epoxide, vinyl, imide, chloro,—(S)_(m)C_(n)H_(2n)—Si—(R)₃ in which m and n are integers between 1 and6 inclusive and the groups R are defined as above.

Non-limiting illustrative examples of a sulphur-containing silane f)include the following:

-   bis[3-(trimethoxysilyl)propyl]-tetrasulfane,-   bis[3-(triethoxysilyl)propyl]disulfane,-   bis[2-(trimethoxysilyl)ethyl]tetrasulfane,-   bis[2-(triethoxysilyl)ethyl]trisulfane,-   bis[3-(trimethoxysilyl)propyl]disulfane,-   3-mercaptopropyltrimethoxysilane,-   3-mercaptopropylmethyldiethoxysilane, and-   3-mercaptoethylpropylethoxymethoxysilane.-   Bis[3-(trimethoxysilyl)propyl]-tetrasulfane (TESPT) and    bis(3-triethoxysilylpropyl) disulphide are preferred.

The sulphur-containing silane f) may be used as such or admixed with aninert filler (for example carbon black) so as to facilitate itsincorporation into the elastomeric composition.

The elastomeric composition according to the present invention may bevulcanised according to known techniques, in particular withsulphur-based vulcanising systems commonly used for diene elastomericpolymers. To this end, in the composition, after a first stage ofthermal-mechanical processing, a sulphur-based vulcanising agent isincorporated together with vulcanisation accelerators and activators. Inthis second processing stage, the temperature is generally kept below120° C. and preferably below 100° C., so as to avoid any unwantedpre-cross-linking phenomena.

The vulcanising agent most advantageously used is sulphur, or moleculescontaining sulphur (sulphur donors), with accelerators and activatorsknown to those skilled in the art.

Advantageously, the elastomeric composition according to the inventionfurther comprises at least one resin cure system. Examples of resin curesystems are phenolic resins, in particular, phenolic resins obtained bycondensation polymerization of a phenol and formaldehyde, commonly knownas resol and novolac. In resol resin, the phenol bears reactive groupssuch as methylol groups.

Advantageously, resin cure systems are used in amounts of from 1 to 15phr, preferably from 2 to 10 phr.

Activators that are particularly effective are zinc compounds, and inparticular ZnO, ZnCO₃, zinc salts of saturated or unsaturated fattyacids containing from 8 to 18 carbon atoms, such as, for example, zincstearate, which are preferably formed in situ in the elastomericcomposition from ZnO and fatty acid, and also BiO, PbO, Pb₃O₄, PbO₂, ormixtures thereof.

Accelerators that are commonly used may be chosen from:dithiocarbamates, guanidine, diphenyl-guanidine, thiourea, thiazoles,sulphenamides, thiurams, amines, xanthates, or mixtures thereof.

The elastomeric composition according to the present invention maycomprise other commonly used additives chosen on the basis of thespecific application for which the composition is intended. For example,the following may be added to said composition: antioxidants,anti-ageing agents, plasticizers, adhesives, anti-ozone agents,modifying resins, fibres (for example Kevlar® pulp), or mixturesthereof.

In particular, for the purpose of further improving the processability,a plasticizer generally chosen from mineral oils, vegetable oils,synthetic oils, or mixtures thereof, such as, for example, aromatic oil,naphthenic oil, phthalates, soybean oil, or mixtures thereof, may beadded to the elastomeric composition according to the present invention.

Preferably, the amount of plasticizer ranges from 2 phr to 100 phr, morepreferably from 5 phr to 70 phr.

The elastomeric composition according to the present invention may beprepared by mixing together the rubber components with the silica fillerand with the silanes d) and f) according to techniques known in the art.The mixing may be carried out, for example, using an open mixer ofopen-mill type, or an internal mixer of the type with tangential rotors(Banbury) or with interlocking rotors (Intermix), or in continuousmixers of Ko-Kneader type (Buss) or of co-rotating or counter-rotatingtwin-screw type.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be further illustrated hereinafter with reference tothe following examples and figures, wherein the attached FIG. 1 shows apartial cross-section view of a pneumatic tyre according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a tyre 1 comprises a carcass structure 2 obtained with aconventional tyre manufacturing process. In fact, the carcass structure2 comprises at least one carcass ply 2 a, the opposite side edges ofwhich are externally folded up around respective annular reinforcingstructures 3, usually known as bead wires.

Alternatively (said embodiment being not shown), each carcass ply 2 ahas its ends integrally associated with the bead wire 3, as disclosed inEP-928 680.

The bead wire 3 is enclosed in a bead 4 defined along an innercircumferential edge of the pneumatic tyre 1 and at which the pneumatictyre engages on a rim (not shown) forming part of the wheel of avehicle.

The tyre 1 comprises a pair of sidewalls 7 which are located in axiallyopposite positions with respect to the carcass structure 2.

The tyre 1 also comprises a tread band 6 in a position radially externalto the carcass structure 2. The tread band 6, comprising the elastomericcomposition of the invention, wherein, at the end of the curing andmoulding steps, a raised pattern is formed for the tyre ground contact.In FIG. 1 the tread band 6 is provided with a plurality of grooves 11which define a plurality of ribs and blocks of the tyre tread pattern.

The tyre 1 further comprises a reinforcing structure 5, usually known asbelt structure, which is positioned between the carcass structure 2 andthe tread band 6. Preferably, the belt structure 5 includes at least tworadially superposed layers 8, 9 of rubberised fabric provided withreinforcing cords, usually of metal material, disposed parallel to eachother in each layer and in crossed relationship with the cords of theadjacent layer, preferably symmetrically disposed with respect to theequatorial plane π-π of the tyre. Preferably, the belt structure 5further comprises, at a radially external position of said belt layers8, 9, at least one further layer 10 of textile or metallic cordssubstantially circumferentially disposed, said cords being spirally andcoaxially wound at a radially outer position with respect to the beltlayers 8, 9.

In the embodiment shown in FIG. 1, the tyre 1 is further provided with alayer 12 of a suitable elastomeric material interposed between the treadband 6 and the belt structure 5. Preferably, the layer 12 has thefunction of improving the adhesion between the tread band 6 and the beltstructure 5.

Finally, in tyres of the tubeless type, i.e. devoid of an air innerbladder, a radially internal elastomeric layer 13, i.e. the liner, ispresent which has imperviousness features to ensure the tyreair-tightness.

The process for producing the tyre according to the present inventionmay be carried out according to techniques and using apparatus that areknown in the art, as described, for example, in EP 199,064, U.S. Pat.No. 4,872,822, U.S. Pat. No. 4,768,937, said process including at leastone stage of manufacturing the green tyre and at least one stage ofvulcanising this tyre.

More particularly, the process for producing the tyre comprises thestages of preparing, beforehand and separately from each other, a seriesof semi-finished products corresponding to the various structuralelements of the tyre (carcass plies, belt structure, bead wires,fillers, sidewalls and tread band) which are then combined togetherusing a suitable manufacturing machine. Next, the subsequentvulcanisation stage welds the abovementioned semi-finished productstogether to give a monolithic block, i.e. the finished tyre.

The stage of preparing the abovementioned semi-finished products will bepreceded by a stage of preparing and moulding the various blends, ofwhich said semi-finished products are made, according to conventionaltechniques.

The green tyre thus obtained is then passed to the subsequent stages ofmoulding and vulcanisation. To this end, a vulcanisation mould is usedwhich is designed to receive the tyre being processed inside a mouldingcavity having walls which are countermoulded to define the outer surfaceof the tyre when the vulcanisation is complete.

Alternative processes for producing a tyre or parts of a tyre withoutusing semi-finished products are disclosed, for example, in EP 928,680,mentioned above, and EP 928,702.

The green tyre can be moulded by introducing a pressurized fluid intothe space defined by the inner surface of the tyre, so as to press theouter surface of the green tyre against the walls of the mouldingcavity. In one of the moulding methods widely practised, a vulcanisationchamber made of elastomeric material, filled with steam and/or anotherfluid under pressure, is inflated inside the tyre closed inside themoulding cavity. In this way, the green tyre is pushed against the innerwalls of the moulding cavity, thus obtaining the desired moulding.Alternatively, the moulding can be carried out without an inflatablevulcanisation chamber, by providing inside the tyre a toroidal metalsupport shaped according to the configuration of the inner surface ofthe tyre to be obtained as described, for example, in EP 242 840. Thedifference in coefficient of thermal expansion between the toroidalmetal support and the crude elastomeric material is exploited to achievean adequate moulding pressure.

At this point, the stage of vulcanising the crude elastomeric materialpresent in the tyre is carried out. To this end, the outer wall of thevulcanisation mould is placed in contact with a heating fluid (generallysteam) such that the outer wall reaches a maximum temperature generallyof between 100° C. and 230° C. Simultaneously, the inner surface of thetyre is heated to the vulcanisation temperature using the samepressurized fluid used to press the tyre against the walls of themoulding cavity, heated to a maximum temperature of between 100° C. and250° C. The time required to obtain a satisfactory degree ofvulcanisation throughout the mass of the elastomeric material can varyin general between 3 min and 90 min and depends mainly on the dimensionsof the tyre. When the vulcanisation is complete, the tyre is removedfrom the vulcanisation mould.

The present invention will be further illustrated below by means of anumber of preparation examples.

EXAMPLES 1-6 Preparation of the Elastomeric Compositions

The elastomeric compositions given in Table 1 were prepared as follows(the amounts of the components are given in phr).

All the components, except sulphur, CBS and DPG80, were mixed togetherin an internal mixer (model Pomini PL 1.6) for about 5 min (1^(st)Step). As soon as the temperature reached 145±5° C., the elastomericmaterial was discharged. The sulphur, and CBS and DPG80 were then addedand mixing was carried out in an open roll mixer (2^(nd) Step).

TABLE 1 Example 1 (*) 2 (*) 3 4 5 (*) S-SBR 100.00 89.41 89.41 78.7578.75 Brominated butyl 2030 — 10.59 10.59 21.25 21.25 Phenolic resin7.29 7.29 7.29 7.29 7.29 Aromatic oil 21.86 25.85 25.85 29.84 29.84Zeosil ®1165 116.58 116.64 116.64 116.69 116.69 AMEO — — 1.46 2.92 5.83Silane X50S 11.66 11.66 11.66 11.67 11.67 DGP 80 1.46 1.46 1.46 1.461.46 CBS 3.35 3.35 3.35 3.35 3.35 Sulphur 1.46 1.46 1.46 1.46 1.46 (*)comparative. S-SBR: solution butadiene-styrene copolymer, with a styrenecontent equal to 20% by weight and a content of vinyl groups equal to60% by weight (product HP752 from Japan Synthetic Rubber) Brominatedbutyl 2030: Bayer (bromine content of 1.8 ± 0.2 wt %) Phenolic resin:octylphenolic resin (Durez ® 29095 by Occidental) Aromatic oil: AgipEsar-90 (produced by Agip) Zeosil ® 1165: precipitated silica with a BETsurface area equal to about 165 m²/g (Rhodia Silica System) AMEO:3-aminopropyl-triethoxysilane (Dynasilan ® AMEO, produced bySivento-Degussa) Silane X50S: bis(3-triethoxysilylpropyl) tetrasulphidesilane comprising 50 wt % of carbon black and 50 wt % ofbis-(3-triethoxysilylpropyl) tetrasulphide (produced by Degussa); DGP80: accelerating agent (diphenylguanidine from Monsanto) CBS:accelerating agent (N-cyclohexyl-2-benzo-thiazylsulphenamide - productSantocure ® CBS by Monsanto)

In the following Table 2, mechanical, dynamic and static characteristicsof the compositions of Table 1 are reported.

TABLE 2 1 (*) 2 (*) 3 4 5 (*) Mooney viscosity 89.8 80.3 78.3 72.3 71.4Scorch time (minutes) 32.510 34.850 27.670 21.530 18.180 CA1 @23° C.(MPa) 1.480 1.300 1.360 1.650 1.770 CA1 @70° C. (MPa) 1.305 1.250 1.2901.530 1.620 CA3 @23° C. (MPa) 5.315 4.510 5.370 6.950 7.730 CA3 @70° C.(MPa) 4.695 4.170 4.840 6.010 6.670 Stress at break (MPa) 12.230 11.30011.080 10.340 11.000 IRHD 10° C. 82.200 80.600 81.500 76.900 71.300 IRHD70° C. 72.100 70.700 67.600 66.100 61.100 Tanδ 10° C. (9%) 0.493 0.5110.510 0.575 0.624 Tanδ 50° C. (9%) 0.256 0.264 0.262 0.272 0.274Abrasion DIN (mm³) 270.2 322.0 275.0 288.0 316.0

The Mooney viscosity ML(1+4) at 100° C. was measured, according to ISOstandard 289/1, on the non-crosslinked materials obtained as describedabove.

The scorch time was measured at 127° C. according to ISO standard 289/1.

CA1 and CA3 are, respectively, the modulus at 100% and a 300%deformation measured according to ISO standard 37-2.

The stress at break was measured at 70° C. according to ISO 37-2 ondumbbell specimens.

IRHD (International Rubber Hardness Degree) at 10° C. and at 70° C.according to ISO standard 48 was measured on samples of said elastomericmaterials cross-linked at 150° C. for 30 minutes.

Tan δ 0° C. and 50° C. are the ratio between the viscous modulus (E″)and the elastic modulus (E′) measured at, respectively, 110° C. and 50°C.;

Abrasion DIN is the amount of compound removed by operating under thestandard conditions given in DIN standard 53516.

With reference to the samples mentioned above, for each of the testedproperty the Applicant calculated the root-mean-square deviation a andthe scattering coefficient V in order to quantify the scattering of themeasured values from the average value.

The comparative composition of Example 1 is a standard elastomericcomposition of the so-called “rain-type” for racetrack.

By partially replacing SBR with a halogenated butyl rubber (comparativecomposition of Example 2) and employing a sulphur-containing silane butnot an aminosilane according to the invention, the static modulus valuesdecrease both at 23° C. and 70° C., indicating a worsening of the tyrehandling, and the abrasion of the tread band is too high for use as atyre tread.

The comparative composition of Example 5 contains the same amount ofhalogenated butyl rubber of that of Example 4 according to theinvention, but a high content of aminosilane which causes difficultiesin the processability due to the decrease of the scorch time.

In addition the abrasion value of the comparative composition of Example5 is substantially as high as that of the Example 2 not containingaminosilane. In other words, exceeding amounts of aminosilane decreasethe abrasion resistance of the tread band.

Also, it should be noted that even if it is desirable to provide acomposition with high values of static modulus, such values should notbe excessive. Excessive static modulus values could compromise a properdeformation of the tread band under the footprint, which is importantfor the grip.

The compositions of Example 3 and 4 according to the invention showparameters suitable for the manufacturing in an industrial plant and areendowed with characteristics such as modulus, hardness and abrasionresistance that are well balanced so as to provide the tyre of theinvention with the sought performance features (grip, handling, roadholding) on wet or icy/snowed surface even under extreme drivingconditions.

Comparing the compositions of the invention with those set forth by theprior art, it is noted that the elastomeric compositions according to EP1 111 004 show poor abrasion resistance and poor tan δ values at 50° C.As for the compositions according to EP 1 236 767, they display very lowvalues of tan δ at 0° C., unsuitable for providing a good grip at lowtemperature, for example on wet or icy/snowed surfaces.

1-39. (canceled)
 40. A pneumatic tyre comprising: a carcass structurewith at least one carcass ply shaped in a substantially toroidalconfiguration, the opposite lateral edges of which are associated withrespective right-hand and left-hand bead wires, each bead wire beingenclosed in a respective bead; a belt structure comprising at least onebelt layer applied in a circumferentially external position relative tosaid carcass structure; a tread band superimposed circumferentially onsaid belt structure comprising a radially outer layer designed to comeinto contact with the ground; and a pair of sidewalls applied laterallyon opposite sides relative to said carcass structure; wherein said treadband comprises an elastomeric material obtained by cross-linking across-linkable elastomeric composition comprising: a) 15 phr to 95 phrof at least one styrene-butadiene rubber; b) 5 phr to 30 phr of at leastone halogenated butyl rubber; c) 0 phr to 60 phr of at least one dienerubber other than a); d) 0.3 phr to 3.5 phr of at least one aminosilanecontaining at least one hydroxy group or hydrolysable group attached tothe silicon atom of the silane; e) 10 phr to 140 phr of at least onesilica filler; and f) 0.5 phr to 25 phr of at least onesulphur-containing silane with at least one hydroxy group orhydrolysable group attached to the silicon atom of the silane.
 41. Thepneumatic tyre according to claim 40, wherein the elastomericcomposition comprises 75 phr to 93 phr of a styrene-butadiene rubber a).42. The pneumatic tyre according to claim 40, wherein the elastomericcomposition comprises 7 phr to 25 phr of a halogenated butyl rubber b).43. The pneumatic tyre according to claim 40, wherein the halogenatedbutyl rubber is a brominated butyl rubber.
 44. The pneumatic tyreaccording to claim 40, wherein the halogenated butyl rubber is obtainedby halogenation of butyl rubber; a copolymer of isobutylene and at leastone comonomer selected from C₄ to C₆ conjugated diolefins; andalkyl-substituted vinyl aromatic comonomers.
 45. The pneumatic tyreaccording to claim 44, wherein the diolefin is isoprene.
 46. Thepneumatic tyre according to claim 44, comprising 1 wt % to 3 wt %isoprene and 97 wt % to 99 wt % isobutylene.
 47. The pneumatic tyreaccording to claim 40, wherein the halogenated butyl rubber has ahalogen content of 0.5 wt % to 4 wt %.
 48. The pneumatic tyre accordingto claim 47, wherein the halogenated butyl rubber has a halogen contentof 0.75 wt % to 3 wt %.
 49. The pneumatic tyre according to claim 40,wherein the halogenated butyl rubber has a molar unsaturation of 0.5% to15%.
 50. The pneumatic tyre according to claim 40, wherein theelastomeric composition comprises from 0 phr to 30 phr of a diene rubberc).
 51. The pneumatic tyre according to claim 40, wherein c) is absent.52. The pneumatic tyre according to claim 40, wherein the diene rubberc) is selected from: polyisoprene; polybutadiene; isoprene/isobutenecopolymers; 1,3-butadiene/acrylonitrile copolymers;styrene/isoprene/1,3-butadiene copolymers;styrene/1,3-butadiene/acrylonitrile copolymers; or mixtures thereof. 53.The pneumatic tyre according to claim 40, wherein the elastomericcomposition comprises 1 phr to 3 phr of an aminosilane d).
 54. Thepneumatic tyre according to claim 40, wherein in the elastomericcomposition the weight ratio between b) and d) components is 2 to 12.55. The pneumatic tyre according to claim 54, wherein in the elastomericcomposition the weight ratio between b) and d) components is 5 to
 8. 56.The pneumatic tyre according to claim 40, wherein the aminosilane d) hasthe following formula (I)

wherein: R₁, R₂ and R₃, which may be identical or different, areselected from hydrogen, hydroxy, C₁-C₁₈ alkoxy groups, C₁-C₁₈ alkylgroups, C₆-C₂₀ aryl groups, C₇-C₃₀ alkylaryl or arylalkyl groups, withthe proviso that at least one of the groups R₁, R₂ and R₃ represents ahydroxy or a hydrolysable group; R₄ is selected from linear or branchedC₁-C₁₈ aliphatic chain groups, C₆-C₂₀ arylene groups, said arylenegroups optionally being substituted with C₁-C₈ aliphatic groups; R₅ andR₇, which may be identical or different, are selected from hydrogen,C₁-C₁₈ alkyl groups; or, when R₅ and R₇ are other than hydrogen, theymay form, together with the nitrogen atoms to which they are attached,5- or 6-membered heterocyclic rings; R₆ is selected from linear orbranched C₁-C₁₈ alkylene groups, C₆-C₁₄ arylene groups, arylene groupsoptionally substituted with C₁-C₁₈ alkyl groups, C₇-C₃₀ alkylenearyleneor arylenealkylene groups, C₃-C₃₀ cycloalkylene groups, saidcycloalkylene groups optionally being substituted with C₁-C₁₈ alkylgroups; and n is a integer from 0 to
 5. 57. The pneumatic tyre accordingto claim 56, wherein all of the R₁, R₂ and R₃ groups are hydrolysablegroups.
 58. The pneumatic tyre according to claim 57, wherein all of R₁,R₂ and R₃ groups are C₁-C₈ alkoxy groups.
 59. The pneumatic tyreaccording to claim 58, wherein all of R₁, R₂ and R₃ groups are C₁-C₃alkoxy groups.
 60. The pneumatic tyre according to claim 56, wherein R₄is a C₁-C₃ aliphatic chain.
 61. The pneumatic tyre according to claim60, wherein R₄ is a C₁-C₃ alkylene chain.
 62. The pneumatic tyreaccording to claim 56, wherein R₇ is hydrogen.
 63. The pneumatic tyreaccording to claim 56, wherein n is
 0. 64. The pneumatic tyre accordingto claim 40, wherein the aminosilane d) is selected from2-aminoethyl-trimethoxysilane, 2-aminoethyl-triethoxysilane,2-aminoethyl-tripropoxysilane, 2-aminoethyl-tributoxysilane,3-aminopropyl-trimethoxysilane, 3-aminopropyl-triethoxysilane,3-aminopropylmethyl-diethoxysilane,N-2-(vinylbenzylamino)-ethyl-3-aminopropyl-trimethoxysilane,N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane, N-2-(aminoethyl)-3aminopropyltris(2-ethylhexoxy)silane,3-aminopropyldiisopropyl-ethoxysilane,N-(6-aminohexyl)-aminopropyl-trimethoxysilane,4-aminobutyl-triethoxysilane, 4-aminobutyldimethyl-methoxysilane,triethoxy-silylpropyl-diethylenetriamine,3-aminopropyltris-(methoxyethoxyethoxy)silane,N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane,N-2-(aminoethyl)-3-aminopropyltris(2-ethylhexoxy)-silane,3-aminopropyldiisopropyl-ethoxysilane,N-(6-aminohexyl)aminopropyl-trimethoxysilane,4-aminobutyl-triethoxysilane, and(cyclohexylaminomethyl)-methyl-diethoxysilane.
 65. The pneumatic tyreaccording to claim 40, wherein the aminosilane d) is3-aminopropyl-triethoxysilane.
 66. The pneumatic tyre according to claim40, wherein the elastomeric composition comprises 40 phr to 110 phr ofsilica filler e).
 67. The pneumatic tyre according to claim 40, whereinthe elastomeric composition comprises at least one carbon blackreinforcing filler.
 68. The pneumatic tyre according to claim 67,comprising 20 phr to 90 phr of said carbon black reinforcing filler. 69.The pneumatic tyre according to claim 40, wherein the elastomericcomposition comprises from 5 phr to 15 phr of a sulphur-containingsilane f).
 70. The pneumatic tyre according to claim 40, wherein thesulphur-containing silane f) has a formula (II)(R)₃Si—C_(n)H_(2n)—X  (II) wherein the R groups, which may be identicalor different, are selected from: hydroxy, alkyl, alkoxy or aryloxygroups or from halogen atoms, on condition that at least one of the Rgroups is a hydroxy, alkoxy or aryloxy group; n is an integer of 1 to 6;X is a group selected from: nitroso, mercapto, amino, epoxide, vinyl,imide, chloro, and —(S)_(m)C_(n)H_(2n)—Si—(R)₃ wherein m and n areintegers of 1 to 6, and the R groups are defined above.
 71. Thepneumatic tyre according to claim 40, wherein the sulphur-containingsilane f) is selected from: bis[3-(trimethoxysilyl)propyl]-tetrasulfane,bis[3-(triethoxysilyl)propyl]disulfane,bis[2-(trimethoxysilyl)ethyl]tetrasulfane,bis[2-(triethoxysilyl)ethyl]trisulfane,bis[3-(trimethoxysilyl)propyl]disulfane,3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane,and 3-mercaptoethylpropylethoxymethoxysilane.
 72. The pneumatic tyreaccording to claim 40, wherein the sulphur-containing silane f) isselected from bis[3-(trimethoxysilyl)propyl]-tetrasulfane andbis(3-triethoxysilylpropyl)disulphide.
 73. The pneumatic tyre accordingto claim 40, wherein the elastomeric composition comprises sulphur or atleast one sulphur donor.
 74. The pneumatic tyre according to claim 40,wherein the elastomeric composition comprises at least one resin curesystem.
 75. The pneumatic tyre according to claim 74, wherein theelastomeric composition comprises 1 phr to 15 phr of the resin curesystem.
 76. The pneumatic tyre according to claim 40, wherein theelastomeric composition comprises 2 phr to 100 phr plasticizer.
 77. Thepneumatic tyre according to claim 76, wherein the elastomericcomposition comprises 5 phr to 70 phr plasticizer.
 78. A cross-linkableelastomeric composition comprising: a) 15 phr to 95 phr of at least onestyrene-butadiene rubber; b) 5 phr to 30 phr of at least one halogenatedbutyl rubber; c) 0 phr to 60 phr of at least one diene rubber other thana); d) 0.3 phr to 3.5 phr of at least one aminosilane containing atleast one hydroxy group or hydrolysable group attached to the siliconatom of the silane; e) 10 phr to 140 phr of at least one silica filler;and f) 0.5 phr to 25 phr of at least one sulphur-containing silane withat least one hydroxy group or hydrolysable group attached to the siliconatom of the silane.